RHABDOCALYPTÜS MOLLIS. 259 



a tube only about half as long as the first and still closed at tlie 

 tip. The third is a long tube, broader but slightly shorter than 

 the first and open at the end ; this I regard in point of age as 

 next to the oldest daughter-person. The fourth is a relatively 

 short blind tube like the second. Finally the fifth, i. e., the 

 uppermost situated near to the margin of the main osculum, is 

 a tube of about the same size as the last but open at the end ; 

 it probably represents a daughter-person younger than the third 

 but older than either the second or the fourth, both of which 

 terminate iu a cul-de-sac indicative of their incomplete develop- 

 ment and may have originated nearly simultaneously. 



Thus far concerning the peculiar external shape which the 

 species may acquire as the result of budding out tubular daughter- 

 persons. 



Now, the gastral cavity of the mother-person — it is scarcely 

 necessary to say — is directly continuous with the like cavities of 

 the daughter-persons. It is very deep and extends close to the 

 basal attachment, so that a solid stalk can certainly not be 

 attributed to the species. Externally, the circumference of the 

 basal attachment may show irregular pad-like thickenings. 



The oscular margin, which is always thin, is generally simple- 

 edged in the daughter-persons. That of the mother-person may, 

 on the other hand, show a varying number of fine, short prostal 

 needles, projecting upwards to a length not exceeding 5 mm. 

 These partly springing from the very edge and partly from the 

 dermal surface adjoining it, may form an inconspicuous and 

 interrupted fringe to the osculum. That diactinic prostalia occur 

 with comparatively greater prominence in the young stage of the 

 sponge, may be concluded from tlie condition presented by the 

 two very small individuals before mentioned. 



